import javax.swing.tree.TreeNode;
import java.util.LinkedList;
import java.util.Queue;

/**
 * \* Created with IntelliJ IDEA.
 * \* User: 冯若航
 * \* Date: 2021/5/17
 * \* Time: 11:27
 * \* To change this template use File | Settings | File Templates.
 * \* Description:
 * \
 */
public class 序列化二叉树 {
    public class TreeNode {
      int val;
      TreeNode left;
      TreeNode right;
      TreeNode(int x) { val = x; }
    }

    // Encodes a tree to a single string.
    public String serialize(TreeNode root) {
        if(root==null){
            return "[]";
        }
        StringBuilder res=new StringBuilder("[");
        Queue<TreeNode> queue=new LinkedList<>();
        queue.add(root);
        while (!queue.isEmpty()){
            TreeNode node=queue.poll();
            if(node!=null){
                res.append(node.val + ",");
                queue.add(node.left);
                queue.add(node.right);
            }
            else{
                res.append("null,");
            }
        }
        res.deleteCharAt(res.length()-1);
        res.append("]");
        return res.toString();
    }

    // Decodes your encoded data to tree.
    public TreeNode deserialize(String data) {
        if(data.equals("[]")) {
            return null;
        }
        String[] vals=data.substring(1,data.length()-1).split(",");
        TreeNode root=new TreeNode(Integer.parseInt(vals[0]));
        Queue<TreeNode> queue = new LinkedList<>();
        queue.add(root);
        int i=1;
        while (!queue.isEmpty()){
            TreeNode node= queue.poll();
            if(!vals[i].equals("null")) {
                node.left = new TreeNode(Integer.parseInt(vals[i]));
                queue.add(node.left);
            }
            i++;
            if(!vals[i].equals("null")) {
                node.right = new TreeNode(Integer.parseInt(vals[i]));
                queue.add(node.right);
            }
            i++;
        }
        return root;
    }

}